#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <string.h>
int main()
{
	char arr[1000] = { 0 };
	scanf("%s", arr);
	int k = strlen(arr);
	int i = 0;
	for (i = 0; i < k; i++)
	{
		int j = 0;
		for (j = i + 1; j < k; j++)
		{

			if (arr[i] > arr[j])
			{
				char tmp = arr[i];
				arr[i] = arr[j];
				arr[j] = tmp;
			}
		}
	}

	for (int i = 0; i < k; i++)
	{
		printf("%c", arr[i]);

	}
	return 0;
}